The present invention relates to a preservative for cooling lubricants.
Presently in the market there is an intensive search for new possibilities of preserving cooling lubricants without formaldehyde. Formaldehyde-free formations have been preserved to date by the use of boric acid (up to 12% by weight), in combination where appropriate with a fungicide. This alternative, however, will be lost in future owing to the classification of boric acid (above a level of 5% by weight) as a category 2 reproductive toxin. At present there are few alternatives to boric acid on the market (e.g. phenoxyethanol, phenoxy-propanols, lactic acid derivatives), but these lag far behind the conventional formaldehyde depot substances in their activity. Consequently there is a need for effective formaldehyde-free and boric-acid-free preservatives for cooling lubricants.
Moreover, the use of known biocides may lead to skin allergies or sensitization on contact with human skin. Biocides having a strongly electrophilic nature (e.g. isothiazolones, organohalogen compounds) in particular, as preservatives or disinfectants, feature prominently in the public debate, and their use is regulated restrictively by the legislator.
DE-C-42 40 674 discloses a deodorizing action of glyceryl monoalkyl ethers of the formula R—O—CH2—CHOH—CH2OH. Further described is a combination of 0.15% by weight phenoxyethanol with 0.135% by weight 1-(2-ethylhexyl) glyceryl ether (Sensiva SC 50), which additionally contains 40% by weight ethanol and 0.015% by weight dibromodicyanobutane.
DE-A-40 26 756 relates to preservatives comprising as synergistic additive substances a mixture of (a) an organic acid, (b) a monophenyl glycol ether and (c) a guanidine derivative. Examples 13 and 14 are concentrates containing more than 60% by weight phenoxyethanol and 15 or 10% by weight, respectively, glyceryl monoalkyl ether. The preservatives of DE-40 26 756 are effective against a variety of bacteria and yeasts.
DE-C-41 40 473 discloses compositions which can be used as skin antiseptics and hand disinfectants and comprise a combination of an aliphatic C1 to C6 alkyl alcohol component and at least one glyceryl monoalkyl ether in aqueous solution. A preferred glyceryl ether is 1-(2-ethylhexyl) glyceryl ether.
DE-A-41 24 664 describes antimicrobial mixtures comprising a synergistic combination of aryl-substituted alkanol with diol. Exemplary diols are glyceryl monoalkyl ethers.
DE-A-100 25 124 discloses preparations which include a combination of glyceryl monoalkyl ether with aryl-substituted alcohol. One preferred aryl compound is phenoxyethanol.
The known applications of glyceryl monoalkyl ethers relate in particular to preparations which are applied to human skin and which therefore must be given a particularly mild formulation. In the case of preservatives for cooling lubricants, in contrast, it is important that the antimicrobial activity is particularly pronounced and that the preservative possesses corrosion control, surface protection and material protection properties and is also stable to oxidation and hydrolysis, stable in colour, and compatible with further ingredients of cooling lubricants. In addition, preservatives for cooling lubricants must be affective against particular microbes, e.g. the yeast Rhodotorula mucilaginosa and the mould fungus Fusarium oxysporum. Moreover, the preservatives for cooling lubricants must be reliably effective over a long period of time, even at elevated temperatures. The requirements asked of a preservative for cooling lubricants, therefore, go a considerable way beyond the requirements normally imposed on a preservative for dermatological preparations.